As the level of technology increases, the options for communications have become more varied. For example, in the last 30 years in the telecommunications industry, personal communications have evolved from a home having a single rotary dial telephone, to a home having multiple telephone, cable and/or fiber optic lines that accommodate both voice and data. Additionally, cellular phones and Wi-Fi have added a mobile element to communications.
To accommodate the new and different ways in which IP networks are being used to provide various services, new network architectures are being developed and standardized. IP Multimedia Subsystem (IMS) is an architectural framework utilized for delivering IP multimedia services to an end user. The IMS architecture has evolved into a service-independent topology which uses IP protocols, e.g., Session Initiation Protocol (SIP) signaling, to provide a convergence mechanism for disparate systems. In part this is accomplished via the provision of a horizontal control layer which isolates the access network from the service layer. Among other things, IMS architectures may provide a useful platform for the rollout of IPTV systems and services.
According to the 3GPP standards organization, multimedia services deployed in IMS networks can be used by IMS users who subscribe to that network. For example, a public service identity (PSI), i.e., one type of SIP uniform resource identifier (URI), enables an IMS user to locate a service within its own IMS network. The PSI is either pre-configured at the terminal, or downloaded from the provisioning node in the IMS network.
Presence information is also available in IMS networks to enable IMS users to know when, for example, their friends are online in their IMS network or in other IMS networks. Such presence information can, for example, be exchanged between two users via the SUBSCRIBE/PUBLISH/NOTIFY mechanism specified by the Open Mobile Alliance (OMA). This presence information includes, among other things, the service capability (SC) at the user's terminal or equipment (UE), e.g., including information about the UE's short message service (SMS) messaging handler, multimedia message service (MMS) messaging handler, instant message (IM) group messaging handler (one-to-many) and IM multi-chat handler. For example, as shown generally in FIG. 1, a first user or user equipment 10 can share information about its service capabilities (SC1-SC3) with a second user or user equipment 12 using presence signaling through its own IMS network 14 and the second user's IMS network 16.
However, this presence information is terminal related only; it provides no network service indication. For instance, suppose that the UE 10 has MMS capability but there is no multimedia message service center (MMSC) in that user's operator's network 14. In this case, the other user 12 will be aware that the UE 10 has MMS capability, but will have no idea whether that user's IMS network operator provides MMS service.